Robert Koch’s Postulates – Past and Present

The Robert Koch Institute in April 2020. Credit: Piotr Orlowski/iStock 

The name Robert Koch is on many people’s lips these days – the work of the Nobel Laureate and co-founder of the Robert Koch Institute still resonates today in very tangible ways.

In his Nobel Lecture in 1905, Robert Koch emphasised the importance of public health measures in the fight against tuberculosis: prompt notification of cases by health authorities, isolation of infectious individuals and rigorous sanitation, including proper attention being paid to coughing hygiene. Sound familiar?  

Anthrax and the Germ Theory of Disease

The germ theory of disease, that is, the idea that illness can be caused by microscopic organisms, was still contentious as recently as the last quarter of the 19^th century. Robert Koch realised very early that diseases such as anthrax, tuberculosis and cholera are infectious and played a huge role in establishing the validity of the germ theory. This, as well as other findings from Koch’s research, were significant not only for their insights into how diseases arise and develop but also because of the implications for human health: if scientists and public health officials could understand disease transmission then they could suggest and implement measures to halt its spread.

Koch’s first major contribution to bacteriology and disease involved uncovering the cause of the fatal disease anthrax. This disease may have already been with us in biblical times, but only with Koch’s work was it proven that the condition was caused by a bacterium. Koch carried out this ground-breaking work in the 1870s while working as medical officer of a district in south-western Germany that was badly affected by the disease. Koch not only established that rod-shaped structures – later named Bacillus anthracis – were responsible for anthrax transmission, but he also succeeded in describing all the stages in the development of the bacterium.      

Tuberculosis and the Importance of Decontamination

After his initial triumph with anthrax, in the 1880s Koch turned his considerable talents and energies to perhaps the greatest scourge of public health in his time: tuberculosis. While Koch’s own work indicated that a microorganism was responsible, the causative agent had not yet been identified.

Identifying Mycobacterium tuberculosis as the causative agent of tuberculosis was to be Koch’s crowning achievement and the Nobel Prize in Physiology or Medicine in 1905: application of what came to be known as ‘Koch’s postulates’ – a set of four criteria that Koch established in 1884, which if met, proved that a given microorganism causes a given disease. These include isolation of causative agent from an organism suffering from disease and disease development once this same isolated agent is introduced to a healthy organism. While Koch’s basic postulates have been modified and amended over the years, they have remained the standard for establishing disease causation and are, in various forms, still being used today.

For Koch, though, as brilliant as it was, the discovery of the microorganism responsible for tuberculosis itself was not the end of his efforts of tackling the disease; he then turned his attentions to how the disease could be prevented and treated. However, his development of a potential drug against tuberculosis turned to be a spectacular failure. Nevertheless, he made very important contributions to preventing the spread of the disease by promoting public health measures.

Cholera – Clean Water as a Prerequisite for Public Health 

Only a couple of years after starting his work on tuberculosis, Koch set this work temporarily aside. At the behest of the German authorities, in 1883 he travelled to Egypt and then to Calcutta, India to investigate outbreaks of cholera, a dreaded disease characterised by diarrhea and dehydration that was to be stopped from spreading to Europe at all costs.  

Through rigorous and meticulous work involving large numbers of autopsies and tracing of the patterns of cases, Koch again succeeded in identifying the comma-shaped bacterium that was responsible for causing cholera – Vibrio cholerae – and discovered that individuals who were susceptible to the disease were becoming infected through the ingestion of contaminated water. Thus, the spread of the disease could be prevented by ensuring access to clean water, and water filtration stopped the disease in its tracks in Calcutta. The importance of water filtration was again demonstrated during an outbreak of cholera in northern Germany some years later, and indeed, provision of safe water remains a cornerstone of efforts to prevent and control cholera to this day.